Set Animation Nodes to work with animated baking
Using this answer, I can make it work via Script node (UV input is a name of UV layer to bake to):



Script itself: (Assign_img.py)

import bpy

image = bpy.data.images["Untitled"]

Object.data.uv_textures[UV].active = True
Object.data.uv_textures[UV].active_render = True

for uv_face in Object.data.uv_textures[UV].data:
    uv_face.image = image